BIVALVIA. 129 



L. pygmaea in being rather more pointed or angulated at the siphoni-lateral margin, with 

 a less elevated umbo, and there is a rather large cartilaginous area and a narrower hinge, 

 the shell also is more tumid. 



The Highgate variety of L. prison is most probably N. minima of 'Mill. Conch.,' 

 t. I 92, fig. 9, which Mr. Sowerby suspected might be the cast of another species. 



7. Leda partim-striata, S. Wood. Tab. XVII, fig. 1, a — c. 



Nccula stiuata, var. J. Sowerby. Trans. Geol. Soc, 2nd ser., vol. v, pi. viii, fig. 12, 1831. 



Spec. Char. L. testa elongato-ovatd. oblatd, tuiuidd, tenui, subaquilaterali ; pedi- 

 regione convexd, siphoni-regione lougiore et obtuse rostratd ; in medio longitudinal iter 

 costatd vcl sulcata ; utrinque laevigata; umbonibus prominulis. 



Shell elongately ovate, oblate, tumid, thin, inequilateral; pedal region convex; siphonal 

 region the longer, laterally compressed, and obtusely rostrated ; central region longitu- 

 dinally ridged, with both extremities smooth ; beaks slightly prominent. 



Length, ird of an inch. 



Localities. Clarendon, Highgate, Potter's Bar, Havcrstock Hill, Alum Bay (Edwards), 

 Hampstead Heath (TFctherctt). 



Although this species appears to have had an extensive geographical range, it is 

 nowhere found in abundance. 



The species to which it approaches nearest is N. amygdaloides, Sow., from which, 

 however, it differs in being only partially covered with ridges, and it is also more inflated 

 and more obtuse. The ventral region is covered with ridges, but the pedal, as also the 

 siphonal sides, are quite smooth. The shell is tumid only in the pedal and central 

 regions ; and compressed on the siphonal side. 



8. Leda propinqua, S. Wood. Tab. XX, fig. 2. 



Spec. Char. L. testa minutd, ovato-subtrigonuld, convexiusculd, sub-inaquilaterali, tenui, 

 laevigata; pedi-regione elongato-ovatd vel semi-ellipticd ; siphoni-regione subrostratd et 

 angulatd ; umbonibus depressis, tctrinque sub-aqualiter declivis, lunula anoque vix perspicuis. 



Shell small, ovately triangular, slightly convex, nearly equilateral, thin, and smooth ; 

 pedal side elongately ovate or semi-elliptical ; siphonal side obtusely rostrated or dorsally 

 angulated ; beaks depressed, with nearly an equal slope on each side ; lunule and corselet 

 scarcely perceptible. 



Length, &ths of an inch ; height, half the length. 



Locality. Colwell Bay (Edwards). 



